Process of separating hydrocarbon mixtures



Nov. 5, 1940.

ChaYge Cooler AsphoJT Sepmrafov Am'me S o\ve"nT I Amine SolvenflI As haH ChiHeY W ax S epcnafrov Oil in solu'l'iop Mlax Chesrer E.An d'rews rocessing or sl'vipping.

INVENTORS Marvell RFenske Patented Nov. 5, 1940 PROCESS OF SEPARATING HYDROCARBON LIIXTURES Chester E. Andrews, Overbrook, and Merrell R. Fenske, State College, Pa., assignors to Riihm & Haas Company, Philadelphia, Pa.

Application July 24, 1937, Serial No. 155,432

Claims.

This invention relates to a process of separating a mixture of hydrocarbons by dissolving the mixture in a methylamine solvent and then changing the dissolving capacity of the solvent 5 to cause the precipitation of a portion of the dissolved hydrocarbons. It relates more particularly to processes of refining mineral oils such as the deasphaltizing and dewaxing of mineral oils."

of the oil being treated to a given temperature it is generally necessary to reduce the temperature of the oil-solvent mixture during treatment to a temperature to degrees Fahrenheit lower than the desired pour point.

The object of this invention is to provide an improved solvent for the dewaxing and deasphalting processes, one that will be more efiective in separating wax and asphalt from the oil 30 and which can be more widely used in petroleum refining and in the treatment of the products resulting from the refining'processes than the solvents now employed by the industry. More generally an object of the invention is to pro- 0 vide a solvent that can be applied generally to the separation of mixtures of hydrocarbons by precipitating a portion hereof.

By the term hydrocarbon as herein used it is intended to include pure hydrocarbons and such additional substances as are substantially hydrocarbon even though other elements such as sulfur, oxygen, nitrogen, halogen, etcJj may be present in small amounts. These additional elements are frequently found in mixtures such as coke oven tar, gas tar, oil mixtures produced by cracking operations, and petroleum or pctroleum fractions to all of which the presentin moval of sufiicient wax to reduce the pour point,

is used to denote semi-fluid forms, sticky or tacky masses, amorphous and soft solids, or granular or crystalline forms, and in addition, the term is used to denote these forms even when they are associated or present along with retained, or ab- 5 sorbed, or occluded liquids.

In general the invention is based upon the discovery that the methylamines have a marked selective solvent action'on hydrocarbons. It has been found that normally solid hydrocarbons 10 and those of high molecular weight are much less soluble in the methylamine than normally liquid hydrocarbons and those of low molecular weight and that the former can be much more efiectively separated jfrom admixtures with the latter than has heretofore been possible with other organic solvents. This general principle has a'variety of practical applications. It can be used to dewax wax bearing oils, to deasphaltize asphalt bearing oils, to separate a wax into waxes of different melting points, to remove oil from oil bearing 20 wax or asphalt, and in general to separate hydrocarbons of higher molecular weight from their admixtures with hydrocarbons of lower molecular weight.

For the purpose of this invention monomethylamine, CHaNHz, dimethylamine, (CHahNH, or trimethylamine, (CH3)3N, or any combination of anytwo or of all three may be used. Of the three methylamines, trimethylamine has the greatest solvent power for hydrocarbons and its use alone is not recommended for the purpose of this invention. Dimethylamine is next in solvent capacity and monomethylamine has the least solvent capacity. By. using various combinations of the three the characteristics of the resulting solvent mixture can be varied over a wide range. It is also/possible to further modify the solvent characteristics by adding to the methylamines other compounds having greater or less capacity for dissolving hydrocarbons and thereby further higher homologues such as octane, nonane, dodecane and mixtures thereof. 91' these various additional compounds that may be used in combination with the methylamines, ammonia merits special mention. Because of the similarity between its chemical and physical properties and the properties of the methylamines with which it forms constant boiling mixtures, it is particularly adapted for mixing with the methylamines where a mixture having a solvent capacity less than that of the pure amine is desired. Whereas trirnethylamine itself is a stronger solvent for hydrocarbons than may be desired in some of the applications of the herein disclosed process, its solvent capacity can be very effectively reduced by the addition of ammonia. used, it is intended to include each of the three methylamines used separately or in combination with each other or with other modifying solvents, particularly of the type herein mentioned.

The methylamines may frequently be separated from the substances with which they are mixed by means of-distillation. However, if this is not particularly feasible, as might be the case when they are' present along with some of the normally gaseous hydrocarbons, then separation may be accomplished by preferential solution and extraction of the methylamines using solvents such as water and the low molecular weight alcohols, so that separation from these latter solvents is now practical by distillation.

In applying the methylamines to the dewaxing of oils the general procedure is analogous to that used with other dewaxing solvents. Essentially it consists in dissolving the oil being treated in a sufiicient quantity of methylamines to hold the liquid hydrocarbons in solution at the temperature to which the mixture is to be reduced, thereafter lowering the temperature to the desired degree, and separating the solidified wax by sedimentation, filtration or centrifuging.

Since the methylamines are gaseous at ordinary temperatures the equipment used in the process must be capable of withstanding the pressures needed to retain them in liquid phase.

The optimum quantity of methylarnine solvent best suited for dewaxing a particular oil will depend upon the oil itself and the composition of the methylamine solvent used.- Because of the wide differences in the composition of oils from difierent fields and in the composition of the various distillates and residues and solvent extraction fractions to all of which-the invention is applicable, no definite ratios for optimum operating conditions can be stated that will be generally applicable. The determination of the best solvent composition for a particular hydrocarbon mixture and the optimum ratio of solvent to oil is however a relatively easy determination if the general principles herein disclosed are understood.

First, it should be understood that the methylamines can be used for solvent extraction, i. e.,

" for the separation of paraffinic type substances from non-paraflinic materials. This use of the methylamines is based upon the principle that non-paraifinic hydrocarbons are more soluble in methylamines than the paraifinic and is fully disclosed in our copending application Serial No.

26,408 filed June 13, 1935, now Patent No.

2,096,725 granted October 26, 1937, of which this application is in part a continuation.

In the dewaxing process it is desirable although not necessary, to avoid the conditions that lead to By the term methylamine as herein the separation of parafllnic and non-paraflinic hydrocarbons. To accomplish this suflicient methylamine solvent is used so that solvent extraction, i. e., the separation of the mixture into two or more liquid phases does not occur at the temperature to which the mixture is lowered to precipitate the wax. This quantity can be easily determined by mixing methylamine solvents of difierent composition with dewaxed oil of the type to be treated in various ratios and lowering the temperature to the point where separation of .liquid phase occurs. At temperatures above the point of separation of phases the oil will be completely soluble in the methylamines. Table I is given to illustrate this procedure. The oil used was a Pennsylvania Long Residuum having a pour point of 10 F. The solvents used were mixtures of technical monomethylamine and dimethylamine, the dimethylamine content of which is indicated in column 1.

TABLE I Approximate temperature of immiscibility, F.

z g i Solvent l .5 Solvent 4 Solvent i Solvent 9 methyl'amine Oil 1 Oil 1 Oil 1 Oil T Degrees Decrees Degrees Degrees Below 35 Below 60 Below 70 Below 60 Below 40 Below 40 Below 20 30 55 Below 40 Below 20 10 40 Below +25 Below +25 +25 In Table II are data on the solubility of white scale wax of 122 F. melting point in, pure dimethylamine and in a mixture of equal parts of dimethylamine and monomethylamine. For comparative purposes data on its solubility in naphtha and a benzol-acetone mixture, known dewaxing solvents, are also included.

TABLE II Solubility of white scale wax in various solvents The data in Tables III and IV show that the methylamine solvents are very effective dewaxing solvents applicable to a wide variety of stocks. It should be pointed out that these data are not to be interpreted to be the best that are possible, or that optimum conditions for each oil were used. More carefully adjusted solvent compositions and proportions for each oil would likely yield even better results. The desired proportion of wax-bearing oil and solvent of suitable composition were mixed in a suitable container at room temperature. Then the mixture was cooled by external cooling to the desired temperature. The oil-methylamine solution was then forced through a filter consisting of canvas weighing 49 ounces to the yard. This canvas held back the solid wax and this was built up as a layer or cake on the canvas. In general the filtering temperature recorded in Table IV was substantially the same as the chilling temperature. The oil-methylamine solution was forced through the canvas by application of inert gas pressure to the slurry, and the pressures recorded in Table IV are these inert gas pressures required to filter the slurry at the rate indicated.

TABLE III Inspection data on stocks used in dewaming These viscosities were obtained by extrapolation on the American Society of Testing Materials (A. S. T. M.) viscosity-temperature chart from the 130 F. and 210 F. viscosities.

TABLE IV At the end of the self-refrigeration period the solvent consisted of. about 50 mol percent of monomethylamine. This is because of the greater volatility of monomethylamine.

TABLE VI Self-refrigeration with the methylamines Percent Time, minutes s? amine evaporated Because of the low denity and viscosity of the methylamines they are particularly adapted to settling or sedimentation operations where the solid phase is separated from the liquid phase Dewaxing with methylamine solvents Solvent to oil ratio=3 to l Solvent composition=dimethylamine with varying weight per cents of monomethylamine Percent mon- Filtering rate R... N. 0.. e r a g gg i time tim mine in ewax o1 waxe 01 per solvent removed ture 1bs./sq. 1n. it per hr LR 30 19 16 5 to 7 2. 4

LR 25 21 10 5 4 to 5 1. 3 LB 26 0 -'5 5 to 7 1. 5

VD 50 28 10 4 1 to 8 1. 6

CS 0 12 15 0 2 to 12 1. 6 LR Naphtha 30 O 0 to 44 0.02

LR =long residuum.

W D=wax distillate.

CS= Cylinder stock.

The data in Table V give properties of the oils listed in Table III after dewaxing with methylamine solvents.

In reducing the temperature to precipitate the. wax due care must be exercised to avoid shock chilling or the introduction of the solution into an environment considerably lower in temperature than the solution. Otherwise the wax precipitated may deposit on the chilled parts and impair its separation and the functioning of the equipment. Chilling may be accomplished either by external refrigeration or internally by a partial evaporation of the methylamines. When internal refrigeration is used the methylamine solvent evaporated can be replaced by additional solvent so as to maintain the desired solvent to oil ratio or in the alternative a sufficient excess can be used in dissolving the oil to provide for the amount vaporized. Table VI shows the rate at which the temperature can be reduced by vaporization of methylamines. The solvent at the start consisted of 58 mol percent monomethylamine and about 42 mol percent dimethylamine.

by allowing it to settle out. As illustrative of this, 173 grams of a wax-bearing Pennsylvania long residuum oil and 2700 c. c. of a methylamine solvent containing about monomethylamineand 75% dimethylamine were placed in a vessel w ere self evaporation of the methyla-mines coi dfiiccur. It should be pointed out that a good po tion of therefrigeration required in this case is for the cooling of the vessel itself and not the methylamine solution. The mixture was chilled, byreducing the pressure and thereby permitting self evaporation of the methylamine. solvent, from 85 F to 0 F. in 40 minutes, an average chilling rate of 2? F. per minute. The volume of solvent-oil-wax mixture was then about 1600 c. c. and the composition of the solvent was estimated to be about 20% moriomethylamine;

This slurry was withdrawn from the vessel and placed in another insulated one where it was allowed to settle for about 10 minutes, at which time the temperature was about 10 F. The supernatant solvent-oil mixture was then removed from the settled wax slurry. After removal of the methylamine from the oil as well as the wax slurry there was obtained 44 grams of wax and 122 grams of oil corresponding to the removal of about 27% of wax. The pour point of the dewaxed oil was 15 F.

Dewaxing by refrigeration is the preferred method of removing wax from waxbearing oils but other methods can be used and various modifications of the refrigeration process are possible. It has been explained above that the three methylamines vary in their capacity to dissolve hydrocarbons. Use may be made of those differences by varying the solvent capacity of the methyl? amine solvent during processing by changing the composition of the methylamine' solvent. In order to facilitate solution of the oil a strong methylamine solvent may be used at the beginning of the process which is thereafter modified by the addition oi a methylamine or other liquid of lower solvent capacity to facilitate precipitation of the wax. It is also possible to combine dewaxing with solvent eqrtraction. As an illustration of how this may be done the data of Tables VII, VIlI,.and IX are presented.

The data of Table VII were secured from a wax bearing substantially asphalt free long residuum stock by extractiton in a packed countercurrent extraction tower employing reflux oil flow. The apparatus and mode of operation used is described by Cannon and'Fenske in "Industrial and Engineering Chemistry," vol. 28, page 1035, September 1936. These data show how the methylamine solvent was able to resolve the original wax bearing residuum into a series 0 oi iractions and how the wax was concentrated in some of the fractions. This segregation of wax in a wholly liquid extraction process is an important feature oi! the methylamine solvents for traction D, comprising 40% of the original material, would not necessarily have to be further dewaxed for some purposes or for use in some blends.

Tana: VII

Batch extraction of an unfiltered wax-bearina Pennsylvania long residuum in a reflux countercurrent extraction tower The extraction temperature was 113 F. and the solvent used was a solution of item to 62 percent dimethylamine in methanol Viscosity Say- P t bolt secondsv it Pour ercen iscos y Enema of charge index 2 9 At 100 At2l0 Original long residuum 100 705 79. 4 110 80 10 368 50. 5 46 10 200 45. 4 96 10 187 45. 4 109 10 '216 47. 8 113 10 302 53. 9 114 10 635 73. 3 108 40 3, 980 234 108. 6 50 Viscosity obtained by extrapolating from viscosities at F. and 210 F. on the A. s. T. M. chart.

For dewaxing, fraction No. 1 is called Cut A,- fractions Nos. 2, 3, and 4 were combined and are called Cut B, fractions Nos. 5 and 6 combined are called Cut C. Table VIII presents data obtained by dewaxing as hereinbefore discussed these several cuts.

waxaeparation. Tbe fllteringrateisthegaiima oi dewaxedoil flowed throuh one an. it. Mill teringareainonehour. Inthiatablethe smalldiflerentialbetweenpourpoint and filter- .ing temperature, the relatively low filtering preasures required. and'the relatively high filtering rates are particularly noteworthy.

Tan: 11

Viscosity data on Pennsylvania long residuum 176011008 (see Tables VII and VIII) WAXY, OIL

Viscosity Baybolt Percent 01 out mum m Viscosity Pour long index point mld'mm 100 1. 210 F.

DEWAXED OIL Viscosity, Saybolt Per cent of out original seconds Viscosity Pour a??? long index point moved 100 F. 210 F.

f Viscosity obtained by and 210 F. on an A. S. T.

These data indicate the manner in which the methylamine solvents may be used to produce neutral and cylinder 01' bright stocks ready for a subsequent step, for example clay filtration, without the necessity of employing distillation. This is an entirely new and novel result.

Even though the methylamines are a. very versatile solvent, they also possess considerable advantages over hydrocarbon solvents for a single process such as dewaxing. The term hydrocarbon solvents is used to include the normally gaseous petroleum hydrocarbons such as propane. The methylamine solvents possess advantages over the hydrocarbon solvents in (a) a higher temperature level may be used for dewaxing with the methylamine solvents and this is economy; (b) the methylamines have higher latent heats of evaporation than hydrocarbon solvents so less solvent needs to be evaporated to reduce or chill extrggolation irom viscosities at 130 F. M. art.

. a solution or oil mixture to a given temperature and this eflects an additional savings; and (0) An additional volume of monomethylarnine was used as a wash solvent to wash the iilter cake.

In dewaxing Cut D, pure dimethylamine was because of the higher temperature levels used in used as the dewaxing solvent. The pour point on Cut D is a viscosity pour point and is not due to the case of the methylamines iordewaxing, special alloys and equipment are not required as K aaaaere they are for the case of the normally gaseous hydrocarbon solvents. A particular virtue of the methylamine solvents is the readiness with which they may be separated from the products obtained. Even from as low boiling a hydrocarbon as benzene separation by distillation may be effected with very littlefractionation. Removal of the amine may also be effected by washing with water or dilute acid. Distillation may be carried out under pressure, and at moderate temperatures where the methylamines may be condensed without compressing, or they may be separated at lower pressures if compression or the equivalent is used. For final stripping of the methylamine from the solid or liquid phases steam or a secondary solvent such as methanol may be used. By processes of fractional distillation the methylamines may then be recovered from the water, or steam or the secondary solvent.

A use of the methylamines in separating solid from liquid hydrocarbons that is similar to dewaxing petroleum oils is the removal of oil from oil bearing waxes. By merely washing an oil bearing wax with methylamines of the proper dissolving capacity substantially all the normally liquid hydrocarbons can be removed therefrom. If desired, however, the wax as well may be dissolved as by raising the temperature or using an amine solvent of maximum dissolving capacity and thereafter precipitated by lowering the temperature or changing the dissolving capacity of the methylamines as hereinbefore explained. In a similar way by controlling the quantity precipitated the wax may also be separated into fractions of higher and lower melting point than the original wax. The higher melting wax precipitates first and may be separated prior to precipitation of the waxes of smaller molecular size.

In deasphaltizing asphalt bearing oils the procedure is somewhat analogous to dewaxing wax bearing oils, but frequently the asphalt is precipitated on the addition of methylamines and it is not generally necessary to cool to the extent required for the separation of wax. Some cooling is however, preferred for it results in sharper and more complete removal of the asphalt. As in the case of dewaxing, a wide range of methylamine solvent combinations and ratios of solvent to oil are available, the most eificient conditions depending upon the particular oil being treated. Generally a larger ratio of solvent to oil than is used for dewaxing is desirable, but in any particular oil it is recommended that preliminary tests be made measuring the solubility of the oil in different methylamine solvent combinations and in various ratios of solvent to oil to determine the optimum conditions of operation. These tests can be made in the same way as heretofore explained in testing for optimum conditions of solvent and solvent-oil ratios in the dewaxing process.

The removal of asphalt from an asphalt bearing oil is illustrated by the following table X. To a relatively wax free and asphalt free long residuum oil having a Saybolt viscosity of 100 F. of 921 seconds, and at 210 F. of 86.8 seconds and a viscosity index of 103, there was added 25% of an asphalt bottoms, giving an asphalt containing oil having a Saybolt viscosity at 130 F. of 1265 seconds, and at 210 F. of 187.1 seconds. By using these viscosities, and the American Society of Testing Materials (A. S. T. M.) viscositytemperature chart, the Saybolt viscosity at 100 F. is estimated to be 3600 seconds for this asphalt bearing oil. On this basis the viscosity index of this asphalt containing oil is about 96 The asphalt bottoms were a very viscous, tacky and sticky, black substance, and were typical of this sort of material as obtained from petroleum in the usual way. Table X relates the treatment of 5 this asphalt containing oil with methylamine solvents. The material removed from the oil as asphalt by the use of these solvents was, for all practical purposes, identical to the material that was added to the original long residuum oil. In 10 some cases it was harder, less sticky and apparently less oil-containing than the original asphalt bottoms, and in character was a solid or semi-solid. It was separated from the methylamine-oil solution by filtering the solution through a fine-mesh metal screen. In certain instances the solid so separated from the solution was somewhat granular in character.

TABLE X Run No.

Solvent D. M. A D. M. A. containin 14.5% metha- Solvent to oil ratio Temperature at which phase separation was made,

Saybolt viscosity of the oil remaining in solution in solvent:

Seconds at 100 F. Seconds at 210 F Approx. percent of asphalt material removed.

The asphalt bottoms above referred to were also treated with several volumes of dimethylamine at its normal boiling point. A hard, granular, dark brown, solid substance resulted and a heavy oil was contained in the methylamine solution phase. This result is characterized as deoiling asphalt, and typifies the treatment of an originally solid or semi-solid substance with methylamine solvents to produce another solidv phase together with a liquid phase.

In Run No. 3 of the above table equally good results can be obtained by dissolving the oil in pure dimethylamine and thereafter modifying the solvent capacity by adding the methanol.

If a particular petroleum oil or fraction contains both asphalt and wax, the problem of which is removed first will depend on the relative quantitles and proportions of each present, the type of oil in which they are contained, and the type of wax and asphalt present. In general, if there are substantial quantities of asphalt present in the particular petroleum oil or fraction, asphalt is removed first since it can be removed at about ordinary temperatures or with only relatively low reductions in temperature. In general, in removing Wax, the temperature required will be 55 of the order of the pour point desired for the oil, provided the pour point is due to the presence of wax and not due to a very high viscosity of the oil, 1. e., to a viscosity pour. When both asphalt and wax are present in substantial quantitles, they may be separated more or less individually by dissolving wholly or in part the oil or fraction in methylamine solvent using a proportion of solvent to oil of the order of three or more volumes of solvent to one of oil. The temperature may also be lowered if necessary. Asphalt will separate out as a solid or semi-solid phase and can be removed from the methylamine solution phase. The composition and proportion of the methylamine solvent may now be readjusted, and the temperature further lowered by external cooling or self evaporation of the methylamine solvent so as to precipitate out Wax as a solid or semi-solid phase, after which it may be removed from the methylamine solution phase and the various phases freed of methylamine solvent by distilling off the solvent.

It is also possible by using the methylamines, to separate wax and asphalt simultaneously as solid or semi-solid substances from a petroleum oil or fraction containing significant quantities of both of these substances. In this case the solvent may consist of monoand di-methylamine mixtures along with suitable proportions of trimethylamine. In general, solvent to oil ratios of the order of three to one to six to one or even greater may be used, and the temperatures-may be below room temperatures. In cases where both wax and asphalt are simultaneously separated from the oil, further separation of these substances from each other may be accomplished by effecting total or partial solution of the wax-asphalt mixture in methylamine solvent of suitable composition and proportion at suitable temperatures. By a fewexperiments on the solubility of wax alone and asphalt alone in methyl-' amine solvent at different temperatures, suitable conditions can be obtained to permit at least a partial separation of the wax and asphalt. It is also possible to effect a segregation of the wax from the asphalt by using solvents where the separation is due principally to the phenomenon of liquid-liquid extraction, the wax being considered the parafiinic substance and theasphalt the non-paraffinic substance. While there is a variety of solvents that can accomplish this, methylamine solvents are suitable for this liquidliquid extraction step. Finally distillation may be used to segregate the wax from the asphalt.

Whether or not it is more desirable to separate wax and asphalt together or individually from petroleum oil or fractions will depend, in a considerable degree, on the nature of the petroleum material.

The drawing illustrates by means of a flow sheet the process herein described. The oil to be deasphalted or dewaxed or both is mixed with methylamine solvent I from 6 in the mixer I. If deasphalting and dewaxing are to be carried out in successive stages, the.composition and quantity of the solvent entering mixer I are adjusted so that the asphalt will precipitate at room temperature or slightly below. The solution then passes through a cooler 2 in which its temperature may be slightly.lowered and thence into the asphalt separator 3 in which the precipitated asphalt is separated from the methylamine-oil solution phase. Any solvent contained in the asphalt is stripped from it. The methylamine-oil solution phase is then mixed with methylamine solvent II from I and passed into the chiller 4. The composition of methylamine solvent II is adjusted so that when added in the proper quantity the mixture has the desired composition for dewaxing. Chilling in chiller 4 may be accomplished by a partial evaporation of the solvent as indicated, or by an indirect cooling means not shown. From the chiller the mixture passes to the wax separator from the solution phase. The

oil in solution leaving separator '5 may be stripped of the methylamine solvent by means not shown or further processed in solution.

If an asphalt-free oil is being processed or if it is desired to remove both asphalt and wax together, cooler 2 and asphalt separator 3 may be by-passed and the composition of the initial methylamine solution adjusted for the simultaneous removal of both wax and asphalt. Or if asphalt alone is to be removed, chiller 4 and wax separator 5 may be eliminated and the oil in the solution phase leaving asphalt separator 3 may be stripped of the solvent.

A further application of the principles of this invention is the use of the methylamines in separating a solid phase from a methylamine solution phase where the materials are lighter petroleum fractions than those normally considered as oil.

. Specifically, fuel oils such as Diesel fuels may be treated at low temperatures to separate as a solid phase the hydrocarbons of higher melting point, thereby lowering the freezing point of the fuel oil. Again, kerosenes and gasoline fractions may be treated with methylamine solvent at low temperatures to separate out solid substances from the methylamine solution. In cases where these petroleum fractions are quite paraflinic in character the solid phase will usually be more paraffinic than the original materials. In general, the use of these methylamine solvents for nonviscous petroleum fractions is usually confined to materials boiling higher than 250 F. at ordinary pressures. -Also, in the preparation of relatively pure hydrocarbons from petroleum, the

. methylamines will be found useful as solvents for the purification of these substances by freezing or fractional crystallization. For example, if normal decane is the desired material, it is possible to prepare a methylamine solvent for this purification by selecting a solvent composition which, at temperatures at least as low as the freezing point of pure normal decane, will just barely dissolve the pure decane, while the decanebearing fraction, or decane concentrate will be more readily soluble. Employing this solvent composition at temperatures of the order of the normal freezing point of decane and lower, will enable fractions richer in decane than the original material to be obtained. As a further application of methylamine solvents to relatively pure hydrocarbon materials, there may be mentioned the separation or purification of anthracene from carbazole. While these two substances possess about equal solubilities in petroleum naphtha, it is to be expected that the nitrogen-containing carbazole would be more soluble than the anthracene in the methylamine solvent.

The foregoing specific descriptions and examples have been given merely as illustrations of methods and procedures for carrying out this invention and it is obvious that the invention extends to various modifications and combinations of these methods and procedures as well as to different oils. It is our intention, therefore, not to limit this invention to the specific illustrations, examples, and descriptions herein given.

In the claims the expression treating the solution to reduce the dissolving capacity of the solvent is intended, to mean that the composition of the methylamine solvent is changed either in the proportion of methylamines or in modifying solvents, that the proportion of the methylamine solvent to the hydrocarbons in solution or those undergoing treatment is changed, or that the temperature is changed. Any one of these steps may be changed at. a time, or any combination of them may be changed at the same time.

It is to be understood that the products as obtained by any of the herein described procedures can either prior to or subsequent to the treatment disclosed be processed by any of the conventional methods used in the industry as for instance, the oils obtained may be clarified by contacting them whil in solution in the methylamine solvent, with various inert absorbent materials such as clays, earths, activated carbon, charcoal and the like.

It is also to be understood that during processing when it is desired to improve or modify the type of crystal or solid phaseobtained from the methylamine solution phase, so as to obtain solids which would permit better filtering rates, or better sedimentation or settling characteristics, or to. obtain solids having less tendency to occlude solution or oil, thereby lessening the tendency to produce oily crystals or solids, socalled crystallization aids may be used along with the methylamine solvent. These aids may be of the Paraflow type or a selected petroleum fraction exhibiting the desired characteristics.

It is claimed:

1. Th process of separating normally solid hydrocarbon from its admixture with normally liquid hydrocarbon which comprises dissolving the mixture in a methylamine solvent containing dimethylamine and monomethylamine in a ratio which permits solution of the, normally liquid hydrocarbon at the temperature used for separating the hydrocarbons, cooling the solution to cause precipitation of the normally solid hydrocarbon, and separating the precipitate from the solution.

2. The process which comprises dissolving in a methylamine solvent containing dimethylamine and monomethylamine a mixture of hydrocarbons derived from petroleum that contains compounds that are normally solid materials, modifying the solvent to reduce the dissolving capacity thereof whereby the normally solid materials are precipitated, and separating the precipitate from the solution.

- 3. The process of deasphaltizing an asphalt bearing oil which comprises mixing the oil with a methylamine solvent containing dimethylamine and monomethylamine, cooling the mixture to cause precipitation of dissolved asphalt, and separating the precipitate from the methylamine solution of the oil.

4. The process 01' dewaxing and deasphaltizing a wax and asphalt bearing oil which comprises mixing the oil with a methylamine solvent containing dimethylamine and monomethylamine, cooling to precipitatedissolved asphalt,

separating the precipitate from the methylamine solution, further cooling the solution to precipitate wax, and separating the wax from the methylamine solution of the oil.

, 5. The process of dewaxing and deasphaltizing a wax and asphalt bearing on which comprises mixing the oil with a methylamine solvent containing dimethylamine and monomethylamine, cooling the mixture to precipitate dis- CHESTER E. ANDREWS. MERRELL R. FENSKE. 

